Why is Drug Addiction so Long Lasting?
One of the hallmarks of drug addiction is that it is chronic and relapsing. This feature is particularly critical because of the apparent difficulty in ‘curing’ addicts, and the production of such myths as ‘once an addict, always an addict’. The development of PET scanning, for example, has allowed us to directly measure the levels of various constituents of the dopamine system in the brain, such as dopamine receptors. Volkow and colleagues (Volkow et al, 1993) at the Brookhaven National Laboratories found that the levels of D2 dopamine receptors are significantly reduced in cocaine addicts, even those who are recently abstinent from cocaine. After 1 month of abstinence, as shown in Figure 4, dopamine levels have not yet returned to normal. Even after 4 months, dopamine receptor levels have not returned to normal. Other studies using other measures of brain activity also show that brain changes can have a long duration, even in abstinent individuals. Thus, many neurochemicals in the br
